Field of the Invention
The invention relates generally to the field of electric motors. In one aspect, the present invention relates to the control and operation of sensorless alternating current induction motors.
Description of the Related Art
The alternating current induction motor (ACIM) is the most popular electric motor used in consumer and industrial applications, notable for the low cost, simple, and robust design since no mechanical commutator or permanents magnets are required. In operation, the motor efficiency and speed are controlled by adjusting the stator voltage according to a motor load by detecting the stator field speed. In the absence of mechanical or electrical contact between the ACIM stator and rotor, there are challenges with determining the relative positions and rotor speeds of the component parts. One position-indicating arrangement is to use sensors to detect a motor component position status as part of the motor control function, but such sensors add cost and increase complexity (due the additional sensors, wiring, connectors, soldering, etc.), reduce reliability (due in part to the sensor connectors that are prone to contamination from dirt and humidity), and are not suitable for applications (e.g., where the rotor is in closed housing and the number of electrical entries must be kept to a minimum, such as in a compressor, or in applications where the motor is immersed in a liquid such as some pumps). To address such shortcomings, sensorless motor control techniques may be used to detect a motor component position status. However, sensorless motor control techniques have a number of drawbacks, including operational complexity, expensive microcontroller requirements, and increased bill-of-materials costs. As a result, the existing solutions for operating alternating current induction motors are extremely difficult at a practical level.